1. Field of the Invention
The present invention is directed to pressure boosters for fluid distribution circuits and to hydraulic distribution circuits incorporating such boosters. More specifically, this invention relates to the enhancement of the flow and pressure characteristics of fluid distribution circuits. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited to use in or as a fluid supply circuit connected to a general water distribution system wherein the flow demands can vary between rather extreme limits. An example of such a system would be a complex of living units where it is necessary to satisfy peak demands for water while simultaneously preventing the pressure from dropping below a predetermined value. Similar problems are presented in, and the present invention is also applicable to, air distribution systems such as ventilation circuits incorporating fans or blowers.
Problems of the type alluded to above have, in the case of hydraulic distribution circuits, previously been solved through the use of hydro-pneumatic pressure booster systems wherein one or more centrifugal pumps were controlled in an on-off fashion. Such prior art systems typically employ an elastic cushion, defined by a pressurized vessel containing a quantity of air, and the volume variations between two predetermined pressures are measured and used to determine the operating cycle of the pump or pumps. Such prior art hydro-pneumatic pressure booster systems have been characterized by relatively high maintenance costs due, in part, to the necessity of periodically reinflating the air cushion; such reinflation being necessitated by micro-leaks or by natural dissolution of the air in water.
In the interest of reducing the size and complexity of pressure booster systems in hydraulic distribution circuits, and also in reducing maintenance requirements and power consumption, it has been proposed to employ permanently operating pressure maintenance pumps. The use of such continuously operating pumps enables elimination of the pressurized vessel since the pump pressure head is added to the pressure of the system. At first glance this would appear to insure adequate pressure in the fluid distribution circuit. However, systems employing continuously operating pressure maintenance pumps have encountered difficulties in insuring peak flows. The provision of grossly oversized pumps to insure adequate peak flows is not an economically feasible solution to these difficulties.
Comparative complex control systems employing both continuously and intermittently operated booster pumps have also been proposed in hydraulic distribution circuits of the type being discussed for purposes of explanation. In such systems there has typically been a functional disparity in size between the continuously operating units and the peak load supplying units and such functional disparities have imposed additional complications on the systems.
A further prior art attempts at solving peak flow problems in hydraulic circuits has envisioned varying the speed of the booster pumps either continuously or in stages. This approach has, however, resulted in extremely complex and expensive systems. This complexity results from the fact that the flow delivered by an electric motor drive centrifugal pump varies with speed thereby making it difficult to multiply the flow provided by a group of such pumps by three or four times as may be encountered during peak load periods. Additionally, adding to system complexity and thus lack of reliability, is the fact that pump compression level varies with the square of pump speed. As a further complication, the power required to drive such pumps also varies in a ratio of the cube of the speed.